1. Field of the Invention
This invention relates to a door closer which has power means to assist the opening of the door and is especially adapted for use in areas frequented by the elderly and infirm. The door closer of the invention is hydraulic and the means for power assist are also hydraulic.
2. Description of Related Art Including Information Disclosed under .sctn..sctn.1.97 to 1.99
There are in the prior art a number of showings of power assist door openers. Usually the power assist is the pneumatic type which, therefore, require the availability of air under pressure. Examples are: U.S. Pat. No. 4,040,144 to Lasier et al, issued Aug. 9, 1977; U.S. Pat. No. 4,429,490 to Richard Zunkel, issued Feb. 7, 1944; and U.S. Pat No. 4,010,572 to Francis C. Peterson, issued Mar. 8, 1977.
Other power assist door openers are: U.S. Pat. No(s). 3,087,720; 3,762,099; 3,470,653; 4,222,147; and 4,339,843.
Lacking in the power assist closers shown in the prior art are adjustable means to activate the power assist feature responsive to the distance which the door is moved out of the frame by the person opening the door. The prior art does include the aforementioned Zunkel patent which discloses a door opener which is activated as the door is moved out of its frame. However, there are no adequate means to adjust the required magnitude of the "bump".
Further, the prior art does not disclose a compact self-contained hydraulic power assist door closer.